Many inborn errors of metabolism cause devastating neurologic disease, an example of which are the lysosomal storage diseases (LSDs). Representative of the LSDs are the mucopolysaccharidoses (MPS), and specifically, beta-glucuronidase deficiency or MPS VII. As yet, systemic treatments for the MPS have no effect on CNS involvement. Thus methods to correct the deficiency in brain should be developed, evaluated, and optimized. During the prior award period we identified key limitations of efficacious application of recombinant viral vectors to brain. Importantly, our data now suggest that the limitations can be overcome, and that a therapeutic response can be achieved when vectors are delivered to functionally impaired brain. In this proposal, we present preliminary data which support our ability to now address two very important hypotheses regarding gene therapy for the CNS manifestations of MPS VII. One, that recombinant vectors based on adeno-associated virus (AAV) will allow for wide-spread expression of recombinant beta- glucuronidase and correction of functional deficits. Two, that global gene delivery, and subsequent recovery of brain function, can be accomplished by intraventricular or peripheral delivery of recombinant AAV vectors. We will use the MPS VII mouse model, which closely recapitulates human patients with MPS VII, to test our hypotheses. Experiments to address these hypotheses will take advantage of our ability to achieve widespread delivery of vector, and hence enzyme, to brain with AAV5, and to target cells lining the ventricles for secretion of enzyme into the CSF with AAV4. These studies will also capitalize on our recent findings that the protein transduction domain of HIV-Tat can be utilized in the context of beta-glucuronidase to improve the biodistribution of this enzyme in brain following expression from transduced cells. This ability of the Tat motif to improve enzyme distribution will also be used in AAV vectors engineered to deliver recombinant enzyme from transduced brain microcapillary endothelia cells, or from the processes of retinal ganglion cells. Finally, we will also evaluate two additional AAV serotypes for their transduction profiles in rodent brain when delivered to the cerebrum, retinal ganglion cells, or cerebellum. The results from these experiments will have relevance beyond MPS VII, with likely application to other lysosomal storage disorders due to deficiencies in soluble lysosomal enzymes.